The accurate determination of expectation values for operators acting
on quantum many-body (QMB) systems at long times remains an open
problem. Much progress has been made for various specific systems of
interest, such as the Ising chain with a quenched transverse
field,[1]} or the Ohmic spin-boson model coupled to a
harmonic non-Markovian environment.[2]} However,
these developments have focused on systems where symmetries and
approximations can be exploited, analytic or exact diagonalization
methods can be used, or matrix product state algorithms can be
employed. Such approaches are either limited in their scope or quickly
become computationally demanding, particularly for systems in more
than one spatial dimension. This is particularly true for the standard
time-evolving block decimation (TEBD) [3]},
time-dependent density matrix renormalization group
(\(t\) -DMRG),[4]} and dynamic density matrix renormalization
group (DDMRG) algorithms.[5]}
